Dramatic reductions in animal-source foods, entailed by many plant-based diets, will worsen already prevalent micronutrient and protein deficiencies, an article published in scientific journal Frontiers in Nutrition this week warns.

The perspective article, authored by Dr Alice Stanton from the Royal College of Surgeons in Ireland and University of Medicine and Health Sciences, examines the reliability of claims that plant-based diets, with very reduced intakes of animal sourced foods (ASFs), will provide nutritional adequacy for all and protection against chronic disease events.

Protections provided by plant-based diets against chronic non-communicable diseases (NCDs) appear to be more strongly associated with reduced intakes of calories and salt, and increased intakes of fruit, vegetables, nuts and whole grains, rather than with reduced intakes of ASFs, Dr Stanton’s analysis indicates.

Her paper highlights numerous questions around the credibility of the science which was used to underpin the anti-meat recommendations of the EAT-Lancet planetary health reference diet published in 2019.

The diet, which made headlines across the world, recommended that just 13 percent of calories in any diet should come from Animal Sourced Foods.

The EAT-Lancet Commission was confident the diet, despite having such a low content of ASFs, would meet all nutritional requirements of both adults and children older than two years.

“This confidence was surprising for a number of reasons”, Dr Stanton writes, pointing to published studies which show that as the percentage of energy coming from ASFs in national food supplies decreases, the prevalence of micronutrient inadequacy increases exponentially.

She also referenced another recently published systematic literature review of the subject which found “clear-cut evidence” that dietary changes aiming to reduce environmental impacts resulted in lower intakes and status of a wide range of micronutrients of public health concern.

And a further published paper which found that decreasing animal-source protein, even to the 50 percent level, led to important declines in the intakes and statuses of vitamin B12 and iodine.

Further studies have identified flaws in the assumptions and methods used, showing that any mortality reduction effect of the EAT-Lancet diet was “no greater than the impact of energy consumption changes that would prevent under-weight, over-weight and obesity alone”.

Strict adherence to the EAT-Lancet reference diet was reported to provide “no additional protection from mortality” by additional research including the Oxford component of the European Prospective Investigation into Cancer and Nutrition study, the Prospective NutriNet-Santé Cohort study, and the Prospective Urban Rural Epidemiology (PURE) study.

The dangers of disregarding best practice in nutritional epidemiology by using low-or very low-certainty evidence in the development of guidelines, or in the calculation of global health metrics, was illustrated by the “very different” Global Burden of Disease (GBD) risk estimates for unprocessed red meat, included in the GBD 2017, GBD 2019 and Burden of Proof (BoP) 2022 studies.

In the GBD 2017 estimates, based on associations with colorectal cancer and diabetes mellitus, the GBD Risk Factor Collaborators stated that diets high in unprocessed red meat were responsible for 25 thousand deaths and 1.3 million Disability-adjusted life years (DALYs), globally.

However, in 2019, the GBD Collaborators reported finding sufficient evidence supporting additional causal relationships of red meat intake with ischaemic heart disease, breast cancer, hemorrhagic stroke, ischaemic stroke and subarachnoid hemorrhage.

Thus, they estimated that 896 thousand deaths and 23.9 million DALYs were attributable to unprocessed red meat consumption. This represented 36-fold and 18-fold increases over the GBD 2017 estimates for deaths and DALYs, respectively.

However, scrutiny by Dr Stanton and others revealed that the evidence for the 2019 estimates came from in-house, newly conducted, systematic reviews and meta-regressions which had not been peer-reviewed nor published, and no assessments of certainty had been conducted.

Many among the scientific community questioned the reliability of these dramatically changed estimates, and, rightly, requested publication of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) compliant reports of the newly conducted systematic reviews.

In response to the scrutiny applied to their report, the GBD collaborators have publicly acknowledged that their 2019 risk estimates of unprocessed red meat for NCD events were erroneously greatly inflated.

Dr Stanton noted that one of the EAT-Lancet Commissioners, Professor Jessica Fanzo, has recently confirmed that their first version of a planetary health diet would result in significant essential micronutrient shortfalls.

However, despite requests to the GBD authors, and to The Lancet’s editorial team and ombudsperson, no corrections have been applied to the published paper, and the 2019 risk estimates remain unchanged on the GBD website.

Hence, considerable doubt remains over the accuracy of these GBD 2019 risk estimates.

Despite these important limitations, the GBD 2019 Risk Factors Study continues to be extensively cited – more than 3650 times in the past four years.

Many have used the GBD 2019 as “primary evidence” for adverse outcomes from the consumption of red meat or processed meat.

“It is of concern that the monthly rate of such publications, using these erroneous estimates, continues to climb,” Dr Stanton writes.

She said it is clear that any evidence that moderate consumption of ASFs is detrimental to human health, “is weak and uncertain”.

It was also clear that the dramatic reductions in ASFs, advised by many plant-based diets, will worsen already prevalent micronutrient and protein deficiencies worldwide.

“Scientists, policy-makers and all involved in the food system should be extremely wary of reports, guidelines or global health estimates that are not rigorously and transparently evidence-based.

“A wide range of sustainably produced, nutrient-rich, animal-and plant-sourced foods, in appropriate evidence-based quantities, should continue to be included in national and international guidelines for healthy diets.

“Further research, finances and effort should be directed toward objective and reliable measurements and improvements in sustainability of each component of the food system; production; processing; distribution; retailing; consumption; and waste management.”

 

Earlier article: Authors acknowledge errors in red meat reduction studies, but still no corrections published